Move clip flag calculation for the new polygon vertices of points and lines
from the renderer to the clipper.

Change-Id: I41ac3647d8e9376586a1011d1cf28d83e9c963a2
Reviewed-on: https://swiftshader-review.googlesource.com/5423Tested-by: Nicolas Capens <capn@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>